Apollo Expeditions to the Moon

CHAPTER 9.2

DETECTIVE WORK ON THE TELEMETRY

What had happened? Ferreting out clues from mission records and the reams of
data recorded from telemetry was a fascinating story of technical detective work. More
than a thousand engineers and technicians at NASA Centers, contractor plants, and
several universities were involved in establishing causes and designing and testing fixes.

The solution for pogo was to modify the pre-valves of the second-stage engines so
that they could be charged with helium gas. This provided shock-absorbing accumulators
that damped out the thrust oscillations.

Finding the culprit that cut off the J-2 engines involved long theorizing and
hundreds of tests that finally pinpointed a
six-foot tube, half an inch in diameter, carrying
liquid hydrogen to the starter cup of the engine. This line had been fitted with two
small bellows for absorbing vibration. It worked fine on ground tests because ice forming
on the bellows provided a damping effect. But in the dryness of space - eventually
simulated in a vacuum chamber - no ice formed because there was no air from which
to draw moisture, and there the lines vibrated, cracked, and broke. The fix: replace the
bellows with bends in the tubes to take up the motion.

With careful engineering analysis and extensive testing we satisfied ourselves that
we understood the problems that plagued Apollo 6 and that the resulting changes were
more than adequate to commit the third Saturn V to manned flight.

At this point we planned that the next Saturn V would be the D mission, launching
Apollo 8 in December with Astronauts McDivitt, Scott, and Schweickart. Their main
objective would be to test the spider-like lunar module then abuilding at the Grumman
plant on Long Island. Early in 1968 we had set the objective of flying the D mission
before the year was out. It was a reasonable target at the time, considering progress
across the program, and would put us in an excellent position to complete the preparatory
missions and have more than one shot at the landing in 1969.

Meanwhile, the command and service modules, after almost two years of reworking
at the North American Aviation plant in Downey, Calif., would have their crucial
flight test on Apollo 7, the C mission, after launch in October 1968 by the smaller
Saturn IB. On board this first manned Apollo mission would be Astronauts Schirra,
Eisele, and Cunningham.

Snug-fitting cocoon housing the Apollo 7 service
module is carefully extracted by workmen
from the Super Guppy, the specially built cargo
transport plane. The SM will be mated with its CM
and then fully tested to confirm compatibility.

Mini TV camera is demonstrated by engineer. On Apollo 7
it produced the first live television broadcast from space, a
seven minute segment with Astronauts Schirra, Eisele, and
Cunningham displaying hand-printed signs, and head colds.
A similar camera was used on Apollo 8.

By midsummer it was apparent that Apollo 7 would fly in October, but that the
lunar module for the D mission would not be ready for a December flight. Electromagnetic
interference problems were plaguing checkout tests, and it was obvious that
engineering changes and further time-consuming tests were needed. After a comprehensive
review in early August, my unhappy estimate was that the D mission would
not be ready until March 1969.